A car started from town A at 7am and reached town B at 9am. Along the same road, a bicycle rider started from town B at 5am and reached town A at 12pm. At what time did they cross each other?

How can I solve this problem?

Let d km be the distance between the cities.
The velocity of the car Vc = d/2 km/h
The velocity of the bicycle Vb = d/7 km/h.
Find the position of the bicycle when the starts and the distance between the car and the bicycle. Let it be d1. Now start counting the time. If they meet at a point x km from the starting point of the car, they take the same time to reach that point. So
x/Vc = (d1-x)/Vb.
Find x in terms of d, then find t.

help

In a certain class consisting of 36 students, some boys and some girls, exactly of one-third the boys and exactly one-fourth of the girls walk to school. What is the greatest possible number of students in this class who walk to school? and how?

In the class, let x boys and (36 - x) girls.
Number of students walking = x/3 + (36-x)/4 ...(1)
Simplify the equation.
Select the values of x, which is less than 36, such that number students who walk to the college must be the whole number.